Roll movement system in a rolling mill

ABSTRACT

Disclosed is a roll driving system for a rolling mill. The roll driving system comprises hydraulic cylinders disposed in parallel between a rolling mill housing and a roll housing for supporting a backup roll and a work roll; load position sensors for detecting load positions of the hydraulic cylinders; means for executing a backward kinematic algorithm which calculates target load positions of the hydraulic cylinders when a target position instruction signal for degrees of freedom of roll movement is inputted from an upper control system, position controllers for controlling positions of the hydraulic cylinders in response to the target load positions inputted from the backward kinematic algorithm executing means; and means for executing a forward kinematic algorithm which calculates positions for the degrees of freedom of roll movement, based on the load positions detected by the load position sensors, and outputs resultant position signals to the upper control system.

TECHNICAL FIELD

[0001] The present invention relates to a rolling mill, and more particularly, the present invention relates to a roll driving system for a rolling mill, which drives rolls with five degrees of freedom to augment strip forming capability, prevent wear of rolls and improve a surface quality of a strip.

BACKGROUND ART

[0002] Conventionally, in a rolling mill generally used in an ironworks, hydraulic cylinders for moving rolls upward and downward to control a thickness of a strip are installed on left and right sides of the rolls in a manner such that they extend in a vertical direction. Also, in order to ensure that roll bodies are rotated through an optional angle with respect to a moving direction of the strip to improve a shape of the strip, driving sections, each of which is constituted by a motor and a straight feeding mechanism, are installed on the left and right sides of the rolls. Moreover, for the purpose of reducing wear of the rolls, motors for moving the rolls in an axial direction are respectively installed on the left and right sides of the rolls.

[0003] However, the conventional rolling mill constructed as mentioned above suffers from defects in that, since it has a serial structural configuration in which driving actuators are installed for respective degrees of freedom of movement, errors are caused in the respective driving sections due to gap formation. As these errors are accumulated, positions errors of the entire rolls are finally generated. Due to looseness induced by the errors and gaps, the rolls are vibrated during rolling, and, due to a difference in roll crossing angle, the strip is likely to meander or produce a camber.

[0004] While actuators for moving the rolls upward and downward are composed of the hydraulic cylinders, being composed of electric motors, remaining driving actuators cannot be placed under a feedback control but can be placed under a set point control. A kinematic structure for preventing occurrence of roll crossing is disclosed in U.S. Pat. No. 4,453,393. In this kinematic structure, a backup roll and a work roll are simultaneously rotated to prevent occurrence of roll crossing. Nevertheless, the kinematic structure has a drawback in that a sliding part to be moved along a straight path is loosened. Also, because the rolling mill disclosed in the patent document basically adopts the serial structural configuration, it preserves defects of the above-mentioned conventional rolling mill.

[0005] Recently, a roll driving system for coping with these problems is disclosed in U.S. Pat. No. 5,924,319. While this type of roll driving system has a structure capable of implementing roll shifting, crossing and bending, since its structure is completely different from that of the conventional system, a fabrication cost cannot but be increased.

DISCLOSURE OF THE INVENTION

[0006] Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a roll driving system for a rolling mill, which drives rolls with five degrees of freedom to prevent wear of rolls and improve a surface quality of a strip.

[0007] In order to achieve the above object, according to the present invention, there is provided a roll driving system for a rolling mill, comprising: a plurality of hydraulic cylinders disposed in parallel between an entire rolling mill housing and a roll housing for supporting a backup roll and a work roll; load position sensors for detecting load positions of the hydraulic cylinders; means for executing a backward kinematic algorithm which calculates target load positions of the hydraulic cylinders when a target position instruction signal for degrees of freedom of roll movement is inputted from an upper control system; position controllers for controlling positions of the hydraulic cylinders in response to the target load positions inputted from the backward kinematic algorithm executing means; and means for executing a forward kinematic algorithm which calculates positions for the degrees of freedom of roll movement, based on the load positions of the hydraulic cylinders detected by the load position sensors, and then outputs resultant position signals to the upper control system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description when taken in conjunction with the drawings, in which:

[0009]FIG. 1 is a perspective view illustrating a state wherein rolls and hydraulic cylinders are installed in a roll driving system for a rolling mill in accordance with an embodiment of the present invention;

[0010] FIGS. 2(a) and 2(b) are schematic views illustrating kinematic layouts of the hydraulic cylinders in the roll driving system according to the present invention;

[0011]FIG. 3 is a schematic view illustrating an actual driving pattern for roll shifting;

[0012] FIGS. 4(a) and 4(b) are schematic views illustrating actual driving patterns for roll offsetting;

[0013]FIG. 5 is a schematic view illustrating an actual driving pattern for roll crossing; and

[0014]FIG. 6 is a block diagram illustrating a control device of the roll driving system according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.

[0016]FIG. 1 is a perspective view illustrating a state wherein rolls and hydraulic cylinders are installed in a roll driving system for a rolling mill in accordance with an embodiment of the present invention. As can be readily seen from FIG. 1, a backup roll 2 and a work roll 3 are received in a roll housing 1 in a state wherein they are supported by a backup roll support part 6 and a work roll support part 7, respectively. A plurality of hydraulic cylinders 4 a through 4 f are mounted to the roll housing 1. Roll housings are connected in parallel to an entire rolling mill housing (not shown). While 3 to 15 hydraulic cylinders can be provided, it is illustrated in FIG. 1 that six hydraulic cylinders are mounted to the roll housing 1. The reason for this is to simplify explanation of the present invention. Consequently, it is to be noted that the present invention is not adversely influenced by varying the number of hydraulic cylinders.

[0017] One ends of the hydraulic cylinders 4 a through 4 f are connected to the roll housing 1 by way of universal joints 5 a through 5 f, and the other ends of the hydraulic cylinders 4 a through 4 f are connected to the entire rolling mill housing by way of universal joints 15 a through 15 f. By the fact that the respective hydraulic cylinders 4 a through 4 f have their independent moving positions of cylinder rods and the roll housing 1 is supported in its entirety by the hydraulic cylinders 4 a through 4 f, the roll housing 1 can be kinematically moved in a space with five degrees of freedom, owing to combination of the moving positions of cylinder rods of the respective hydraulic cylinders 4 a through 4 f.

[0018] FIGS. 2(a) and 2(b) are schematic views illustrating movement of the rolls driven by the plurality of hydraulic cylinders, wherein FIG. 2(a) illustrates movement of the rolls driven by four hydraulic cylinders, and FIG. 2(b) illustrates movement of the rolls driven by six hydraulic cylinders. In FIGS. 2(a) and 2(b), an upper plate (serving as the entire rolling mill housing represented by an upper large circle) is fixedly maintained, and a lower plate (serving as the roll housing represented by a lower small circle) is freely moved in the space in conformity with the movement of the hydraulic cylinders. The hydraulic cylinders are located in parallel between the upper entire rolling mill housing and the lower roll housing. An interval and an angle of the hydraulic cylinders are determined by a range of movement for each degree of freedom.

[0019] Generally, degrees of freedom of movement required upon performing a rolling process include roll shifting, roll offsetting, roll up-down, roll crossing, and roll leveling.

[0020] As shown in FIG. 3(a), the roll shifting is implemented in a manner such that a roll is driven in an axial direction to reduce wear of the roll upon rolling a strip. Through implementing the roll shifting by simultaneously moving an upper roll housing and a lower roll housing in the rolling mill in the same direction and over the same distance, as the strip is moved sideward upon being rolled, it is possible to align the strip on a center line of a moving path.

[0021] As shown in FIG. 4(a), the roll offsetting is implemented in such a way as to offset centers of the upper and lower rolls from a vertical line. By implementing the roll offsetting, as a shearing stress is induced in the strip, a surface quality of the strip is improved. Generally, as best shown in FIG. 4(b), if the roll housing is moved in a moving direction of the strip or in a reverse direction, as increased or decreased tension is applied to the strip, it is possible to control tension.

[0022] The roll up-down is implemented in a manner such that the roll housing is driven upward or downward to control a thickness of the strip. As shown in FIG. 5, the roll crossing is implemented in a manner such that the left and right sides of the roll are independently driven upward or downward to adjust left and right roll gaps.

[0023] Strip forming capability of the rolling mill is determined by the above-described five degrees of freedom.

[0024]FIG. 6 is a block diagram illustrating a control device of the rolling mill having five degrees of freedom. While the control device for the rolling mill having installed therein six hydraulic cylinders is illustrated in FIG. 6, a person skilled in the art will readily recognize that the present invention is not limited by the number of the hydraulic cylinders.

[0025] As shown in FIG. 6, the control device comprises a backward kinematic algorithm executing part 16 which receives position instructions for degrees of freedom of roll movement and calculates target load positions of the hydraulic cylinders 4 a through 4 f, hydraulic cylinder position control arrangements 20 a through 20 f, and a forward kinematic algorithm executing part 17 which receives load positions of the hydraulic cylinders 4 a through 4 f from hydraulic cylinder position sensors 11 a through 11 f and calculates current positions for the degrees of freedom of roll movement.

[0026] The hydraulic cylinder position control arrangements 20 a through 20 f respectively comprise hydraulic cylinder position controllers 15 a through 15 f, servo valve amps 14 a through 14 f, servo valves 13 a through 13 f, the hydraulic cylinders 4 a through 4 f, and the hydraulic cylinder position sensors 11 a through 11 f. It is to be noted that the hydraulic cylinder position control arrangements 20 a through 20 f are independently provided for the hydraulic cylinders 4 a through 4 f, respectively.

[0027] If target positions of the roll are determined for each degree of freedom of roll movement in an upper rolling mill control system and transmitted to the backward kinematic algorithm executing part 16 of a roll driving section, the backward kinematic algorithm executing part 16 calculates the target load positions of the hydraulic cylinders 4 a through 4 f, and then outputs the calculated target load positions to the hydraulic cylinder position controllers 15 a through 15 f.

[0028] Calculated results of the backward kinematic algorithm executing part 16 vary depending upon the number, a length and a kinematic layout of the hydraulic cylinders 4 a through 4 f. The hydraulic cylinder position controllers 15 a through 15 f detect current load positions of the hydraulic cylinders 4 a through 4 f through the hydraulic cylinder position sensors 11 a through 11 f attached to the hydraulic cylinders 4 a through 4 f, calculate control errors, and then transmit the resultant signals to the servo valve amps 14 a through 14 f by the medium of a control algorithm. The servo valve amps 14 a through 14 f actuate the servo valves 13 a through 13 f to drive the hydraulic cylinders 4 a through 4 f thereby to conduct position control. The forward kinematic algorithm executing part 17 calculates positions for the degrees of freedom of roll movement, and then outputs resultant position signals to the upper rolling mill control system.

[0029] Since the upper rolling mill control system drives the roll depending upon the transmitted degrees of freedom of roll movement, roll shifting is enabled so that the roll is driven in the axial direction to reduce wear of the roll upon rolling the strip. By implementing the roll shifting in a manner such that the upper work roll and the lower work roll of the rolling mill are simultaneously driven in the same direction by the same distance, the strip can be moved sideward while performing a rolling process, and in this way, it is possible to prevent the strip from meandering. Also, by implementing the roll offsetting so that the centers of the upper and lower rolls are offset from the vertical line, a shearing stress is induced in the strip, and as a result, a surface quality of the strip is improved. In the case that while the upper and lower rolls are simultaneously moved in the moving direction of the strip or in the reverse direction while performing the rolling process, it is possible to apply increased or decreased tension to the strip, whereby tension control is enabled.

[0030] Upon implementing the roll up-down, as the roll is driven upward or downward, it is possible to adjust a thickness of the strip. In the case of implementing the roll crossing, as the roll bodies are rotated by an optional angle with respect to the moving direction of the strip, it is possible to improve a shape of the strip. Also, as described above, the roll leveling is implemented in a manner such that the left and right sides of the roll are independently driven upward or downward to adjust left and right roll gaps.

[0031] Industrial Applicability

[0032] As apparent from the above description, the roll driving system for a rolling mill, according to the present invention, provides advantages as described below. Since rolls are driven with five degrees of freedom in a manner such that positions are calculated in correspondence to the respective degrees of freedom of roll movement, it is possible to improve a surface quality of a strip, and secure control over tension, thickness, meandering, camber, contour, etc. Also, because error accumulation, which is caused by a driving mechanism of the conventional serial structural configuration and looseness of a sliding guiding surface, is avoided, vibration and meandering of the strip can be markedly suppressed. Further, due to the fact that a rolling pressure applied to the strip during rolling and shock generated upon passage of the strip are propagated to hydraulic cylinders in an axial direction, a load-resistant rigidity is increased. Moreover, by the fact that working fluid in the hydraulic cylinders absorbs high-frequency vibration and momentary shock, vibration and shock damping capability is significantly augmented. 

1. A roll driving system for a rolling mill, comprising: a plurality of hydraulic cylinders disposed in parallel between an entire rolling mill housing and a roll housing for supporting a backup roll and a work roll; load position sensors for detecting load positions of the hydraulic cylinders; means for executing a backward kinematic algorithm which calculates target load positions of the hydraulic cylinders when a target position instruction signal for degrees of freedom of roll movement is inputted from an upper control system; position controllers for controlling positions of the hydraulic cylinders in response to the target load positions inputted from the backward kinematic algorithm executing means; and means for executing a forward kinematic algorithm which calculates positions for the degrees of freedom of roll movement, based on the load positions of the hydraulic cylinders detected by the load position sensors, and then outputs resultant position signals to the upper control system.
 2. The roll driving system as set forth in claim 1, wherein the hydraulic cylinders are 3 to 15 in number.
 3. The roll driving system as set forth in claim 1, further comprising: servo valves for driving the hydraulic cylinders in response to signals inputted from the position controllers.
 4. The roll driving system as set forth in claim 1, wherein the target load positions calculated by the backward kinematic algorithm executing means vary depending upon the number, a length and a layout of the hydraulic cylinders. 